Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
chiz = [[] for _ in range(w)]
cnt = 0
for _ in range(h):
    tmp_list = input()
    for i in range(w):
        if tmp_list[i]=='.':
            cnt += 1
        chiz[i].append(tmp_list[i])
dq = deque([(0,0)])
chiz[0][0] = 0
while dq:
    i,j = dq.popleft()
    for e in [(1,0),(-1,0),(0,-1),(0,1)]:
        if i+e[0]>=0 and i+e[0]<w and j+e[1]>=0 and j+e[1]<h:
            if chiz[i+e[0]][j+e[1]] == '.':
                chiz[i+e[0]][j+e[1]] = chiz[i][j] + 1
                dq.append((i+e[0],j+e[1]))
try:
    print(cnt-chiz[w-1][h-1]-1)
except:
    print(-1)